US 2009/0192961 A1 describes a system for adapting the bit rate of a media stream based on user interest. Collected biometric data can be used to determine a user's emotional interest and optionally adjust the bit rate of media and/or present navigation options to one or more selected portion of the stored media. Biometric data can include heart rate, respiratory rate, galvanic skin response, pupil dilation, blood pressure, body temperature and the like. Biometrics can be collected from sensors, which can include electrodermal sensors, microphones, thermometers, accelerometers and the like. In an embodiment, changes in user interest can trigger a variable bit rate encoder to adjust the bit rate processing of captured audio/video based on configuration options. For example, a digital camera can obtain biometric data during picture capture. When user interest is detected as high, the image resolution and megapixel count can be increased, storing the picture as a high fidelity image. Collected biometric data can be stored as metadata in the images for use in playback and navigation.
A problem of the known system is that it is limited to the biometric data that can be obtained at the time of capture. Only the biometric data characterizing the person attached to the sensor is obtained. Additional biometric sensors of the described type are required for each additional person, and each person must co-operate.